Metallic shoe for truss-bridges



UNITED STATES PATENT OFFICE.

D. H. MORRISON,

OF DAYTON, OHIO.

METALLIC SHOE FOR TRUSS-BRIDG-ES.

Specification of Letters Patent N o. 20,082, dated April 27, 1858.

To all whom it may concern:

Be it known that I, DAVID H. MoRIusoN, of Dayton, Montgomery county,Ohio, have invented a new and useful Improvement in Wooden Truss-Framingfor Bridges and other Similar Structures; and I hereby declare thefollowing to be a full and exact description of the same, referencebeing had to the accompanying drawings, making part of thisspecification.

The shrinkage of timbers in cross section causes trusses formed of greentimber to become rapidly loose or rickety when the braces rest or bearagainst the sides of the other parts of the trusses.

The elongation or enlargement of the panels of a truss by shrinkagerenders both main and counter-braces too short and the consequentsettling of the truss which keeps the main braces tight elongates thediagonal of the panel in the direction of the counter brace and itbecomes entirely useless.

My invention relates to a provision whereby a. truss bridge or otherwooden truss frame is preserved from the deleterious effects ofshrinkage.

In the accompanying drawings Figure l is a side view of a portion of atruss bridge embodying my improvement. Fig. 2 is a transverse sectionthereof. Fig. 3 is a perspective view of the shoe on an enlarged scale.Fig. 4 represents a modification of the shoe, adapted for light work.

A, and B, are respectively the upper and lower chords.

O, are the posts. The notches l, in the sides of the posts, which upholdthe lower chords, feather out at their upper parts to afford asufficient depth of shoulder to support the rear flange of the shoe,hereafter described.

D, are the main brace timbers and E, are the counter braces.

The principal feature of my improvement consists in a device fortransferring the thrusts of the braces of a truss wholly to the ends ofthe fibers of the posts and chords conjointly, instead of sustainingthem wholly or partially on the sides of the fibers. For this purpose Iemploy a cast iron (or other metallic) shoe or angle piece G H I J K,whose longitudinal contour, in its most perfect form is a right angledtriangle equal in length to the width of the post and the two sidesforming the right angle bearing about the same proportion to thehypotenuse that the length and height of the panel do to its diagonal.

The position of the'shoe or angle piece in the truss is with its longestside or hypotenuse against the upper or lower chord as the case may be,and at the side of and in contact with the post, to which it is securedby a bolt L. The sloping sides of the casting consist of two plates G,H, one of which (G) forms such an angle with the chord, as to afford tothe end of the brace a bearing surface at right angles or nearly so toits fibers. The plate H, is merely a rib or stay, which together withthe ribs L, transfer the thrust of the brace to the chord and post.

Projecting from the sole of the shoe and occupying a transverse gain ornotch in the top of the lower chord or the bottom of the upper chord asthe case may be, is a flange I, whose bearing surface is at right anglesto the fibers of the chord. J, is a flange projecting horizontally fromthe rear side of the shoe into a suitable gain in the post so as topresent a bearing surface c, at right angles to its fibers. A flange K,serves to stiffen the shoe and prevent the contact of the brace andpost, to obviate decay. By forming the surface a, atright angles to thediagonal of the panel and also of the main brace (see dotted line)facility of inserting the latter is obtained while preservingsubstantially the main feature of the improvement.

The above form of shoe has been employed effectively in bridges of 100feet span and upward, but for those of less spa-n (eX- cepting railwaybridges) and for handrailing on suspension bridges, truss partitions,trest-les and gates the shoe may consist simply of a plate G, whoseflanges I', J', are gained into the post and chord in the manner shownin Fig. 4.

I am aware that various descriptions of framing have been constructedwith metallic shoes furnished with lugs, the ofce of which is topreserve the shoe from displacement on the timber upon which it rests,but I know of none in which such a disposition and combination ofbearing surfaces is employed as to sustain the thrust on the ends of thefibers in three different directions so that the shoe is prevented fromfollowing the lateral shrinkage of either the chord or post with whichit comes in Contact.

I do not confine myself to three bearing purpose of preventing theinjurious effects of shrinkage,-there being on every shoe at least threesuch bea-ring surfaces; one each for the chord, post and brace.

In testimony of which invention I hereunto set my hand.

D. H. MORRISON.

Attest:

GEO. H. KNIGHT, CLEMENT E. BABB.

